The current Otway basin fields under development consist of Minerva, Casino Geographe and Thylacine.
Otway basin: Minerva
Minerva came on stream in early 2005. The field is located in VIC/L22 permit, approximately 10km from Port Campbell in 60m of water. The development is operated by BHP Billiton (90%) on behalf of Santos (10%). It was discovered in 1993 by the Minerva 1 exploration well.
Up to year end for 2007, the latest for hich figures are available, the field was producing at a rate of 130-140 terajoules of sales gas per day (TJ/d), and 520-575 barrels per day (gross) of stabilised condensate.
The AU$255 million Minerva development consists of two subsea well completions producing through 10km of 10in pipeline to the shore. The pipeline crosses the shore via a directionally-drilled crossing under the beach and then moves to the gas processing plant a further 4.5km inland.
Otway basin: Casino
The Casino field was discovered in 2002 by the Casino 1 exploration well and contains estimated recoverable reserves of 290 billion ft³ of dry natural gas. The field lies in the VIC/P44 permit, 250km south-west of Melbourne in 70m of water.
The $200 million development is operated by Santos (50%) on behalf of AWE (25%) and Mitsui (25%). Full production began in February 2006, and at year end 2007 it was producing at 96 terajoules per day and 96 barrels of condensate per day.
At the moment, the field has two production wells completed with subsea wellheads and will produce through 38km of 12in pipeline to the shore. The pipeline crosses the shore via a directionally drilled crossing under the beach and then moves to the Iona gas processing plant a further 12km inland. Production is scheduled to commence in the first quarter of 2006.
Otway basin: Geographe and Thylacine
The largest development in the area is the so-called Otway Gas Project – the $1.1 billion development of Thylacine and Geographe. It is operated by Woodside (51.55%) on behalf Origin Energy (29.75%), Benaris (12.7%) and CalEnergy (6%).
Thylacine lies in the Tasmanian permit T/30P, about 70km south of Port Campbell. Geographe, in Victorian permit Vic/P43, will be connected to the main offshore pipeline in a later development phase.
The field was discovered following the 1999 Investigator 3D seismic programme. The Thylacine-1 exploration well drilled in May 2001 and discovered gas in a 281m gross gas column. In August 2001, the company drilled the Thylacine-2 appraisal well, which found a 230m gross gas column. The production tested well at 28 million scf/d from two zones. Meanwhile, in May/June 2001, Woodside spudded the Geographe-1 exploration well and discovered gas in a 240m gross gas column.
The development included:
- Wellhead platform on the Thylacine reservoir
- Subsea manifold on the Geographe reservoir
- Subsea pipeline from the wellhead platform to the Victorian coast
- Onshore gas plant located near Port Campbell.
Over the life of the project, the Thylacine and Geographe gas fields are expected to supply 950 billion ft³ of raw gas, 885PJ of sales gas, 12.2 million barrels of condensate and 1.7 million tonnes of LPG. The Otway Gas Project will initially produce about 60PJ of sales gas a year. Production began in September 2007, initially at about 60PJ od sales gas a year.
Technip was awarded a €200 contract for the engineering, procurement, installation and construction of the onshore gas processing plant and onshore pipeline, and the offshore platform facilities. The offshore pipelay and subsea tie-in has been carried out by Allseas. The horizontal directional drilling shore-crossing contract has been awarded to DrillTec.
Maersk Contractors won the contract for drilling at least four production wells using the Maersk Guardian jack-up drilling rig.